The use of double metal cyanide complex catalysts ill the preparation of high molecular weight polyols is well-established in the art. For example, U.S. Pat. No. 3,829,505, assigned to General Tire & Rubber Company, discloses the preparation of high molecular weight diols, triols etc., using these catalysts. The polyols prepared using these catalysts can be fabricated to have a higher molecular weight and a lower amount of end group unsaturation than can be prepared using commonly-used KOH catalysts. The '505 patent discloses that these high molecular weight polyol products are useful in the preparation of nonionic surface active agents, lubricants and coolants, textile sizes, packaging films, as well as in the preparation of solid or flexible polyurethanes by reaction with polyisocyanates.
In order to prepare polyols using double metal cyanide complex catalysts, it is necessary to employ propoxylated initiators as reactants since non-propoxylated initiators such as glycerine fail to react with propylene oxide in the presence of double metal cyanide complex ("DMC") catalysts. This lack of reaction is apparently due to the insolubility of the DMC catalyst in the initiator.
In view of this problem, propoxylated initiator precursors are conventionally prepared by the reaction of propylene oxide with the initiator (such as glycerine) in the presence of a potassium hydroxide ("KOH") catalyst. Unfortunately, the presence of even a small amount of KOH catalyst in the propoxylated precursor kills the catalytic activity of the DMC catalyst utilized in the subsequent polyol-forming reaction. Therefore, removal of the KOH catalyst from the propoxylated precursor must be effected prior to the use of this precursor in the DMC catalyzed production of polyols.
Removal of the KOH catalyst from the propoxylated precursor can be accomplished by any one of several methods described in the patent literature; however, the KOH catalyst removal step is expensive and time-consuming. Accordingly, a new method for providing the desired propoxylated precursors that does not utilize KOH catalyst, and does not require any catalyst separation step prior to the use of these precursors in the DMC catalyzed production of polyols, would be highly desired by the polyol manufacturing community.